The present invention relates to a bolt assembly for interengaging two relatively movable elements.
Interlock bolt systems are well known which are intended to prevent access to the interior of for example a machine enclosure unless the bolt assemblies are disengaged after the enclosed machine has been de-energised, or to prevent the doors of for example a railway vehicle from being opened unless the bolt assemblies have been disengaged after the vehicle is stationary. The known bolt assemblies comprise two components one of which is connected to one element of an enclosure such as a door frame and the other of which is connected to another element of the enclosure, for example a door. The first component includes a bolt displaceable between engaged and disengaged positions, and the second component comprises a socket into which the bolt may be extended when the two components are in an appropriate position relative to each other and the bolt is moved to the engaged position. The position of the bolt is controlled for example by manipulation of a security key or energisation of an interlock circuit so as to prevent opening of the enclosure except in predetermined safe conditions.
It is known to provide bolt assemblies which are operated by keys, the operating keys being trapped by the key operated mechanism unless the associated components of the bolt assembly are in a predetermined configuration in which it is assumed the components are locked together. For example, in a bolt assembly for a machine enclosure, the same key may be used to control both machine energisation and bolt position. The key is trapped in the bolt assembly unless the bolt has been extended, the expectation being that if the bolt is extended the enclosure door is locked shut. Once the door has been locked, the key can be removed from the bolt assembly and used to energise the machine. One of the problems with such bolt assemblies is that, if a key is actuated to extend the bolt in circumstances where it is presumed that the two components of the bolt assembly are interengaged by the bolt but in fact the two components are not interengaged, unsafe conditions may prevail despite the bolt being extended. It will of course be appreciated that in a two component bolt assembly it is not sufficient to ensure simply that the bolt is extended as it may be that the bolt when extended has not engaged the other component of the assembly. Similar problems can arise with for example vehicle doors, where it is not sufficient to sense only bolt extension to check whether or not a door has been locked shut. It is also necessary to be sure that the door is shut so as to be engaged by the extended bolt.
In one known interlocked bolt assembly, a first component of the assembly carries a key actuated lock mechanism and the second component of the assembly carries a bolt or catch. The key is retained in the first component unless it has been turned to a key-release position. The key is prevented from being turned to the key-release position unless the bolt or catch has been extended from the second component into engagement with the first component. Such an arrangement functions satisfactorily, but each of the two components supports a relatively complex mechanism which in some applications is inconvenient. Furthermore, it is difficult to provide an emergency release function, enabling persons trapped within an enclosure to exit the enclosure without use of the keys.
It is an object of the present invention to obviate or mitigate the problems outlined above.
According to the present invention, there is provided a bolt assembly for interengaging two relatively moveable elements, the assembly comprising a first component which in use is connected to one element, and a second component which in use is connected to the other element, the first component including a bolt displaceable between engaged and disengaged positions, and the second component comprising means for engaging the bolt to interengage elements to which the components are connected when the first component is in a predetermined position relative to the second component and the bolt is in the engaged position, wherein the first component comprises a magnetically releasable latch mechanism arranged to latch the bolt in the disengaged position, and the second component comprises at least one source of magnetic flux arranged to release the latch when the first component is in the predetermined position relative to the second component.
The magnetically releasable latch mechanism may comprise one or more permanent magnets biased to a latch engaging position and the magnetic means may comprise one or more permanent magnets arranged to displace the or each permanent magnet of the latch mechanism to a latch releasing position when the first component is in the predetermined position relative to the second component. For example, two parallel bar magnets may be provided in the first component and two permanent bar magnets may be provided in the second component, the permanent magnets of each component being of the same polarity such that the permanent magnets of the first component can only be displaced by exposure to magnetic fields generated by two further permanent magnets or sources of magnetic flux producing an equivalent magnetic field to two permanent magnets. This makes it difficult for the latch mechanism to be released in an unauthorised manner.
The at least one permanent magnet of the latch mechanism may be biased to the latch engaging position by a spring or a further permanent magnet. The bolt and the or each permanent magnet may each define slots and a locking member may be located between the bolt and the or each permanent magnet so as to engage either in the bolt slot or in the adjacent magnet slot. If the locking member is engaged in the magnet slot, the bolt is free to move between engaged and disengaged positions. If the locking member is engaged in the bolt slot, the bolt is retained in the. disengaged position.
The bolt may comprise a cylindrical member slidably received in a cylindrical bore. Alternatively, one or more pivotally mounted locking arms may be provided, one end of the or each locking arm defining a bolt. The pivotally mounted arm may be mechanically coupled to a solenoid energisable to pivot the locking arm and a switch may be provided for sensing the pivotal position of the locking arm.